AB1233 CHARACTERISTICS OF PEDIATRIC MPO AND PR-3 ANCA ASSOCIATED VASCULITIS- SINGLE CENTER EXPERIENCE FROM CENTRAL CALIFORNIA
Authors: D. Singh, S. Sukesh
Journal: Annals of the Rheumatic Diseases (2022)

Background ANCA-associated vasculitides (AAV) are rare in childhood and characterized by necrotizing inflammation in small to medium sized vessels. Most of the available literature in children focuses on clinical subtypes Granulomatosis with Polyangiitis (GPA), Microscopic Polyangiitis (MPA), and Eosinophilic Granulomatosis with Polyangiitis (EGPA). Adult studies have demonstrated differences in clinical outcomes based on myeloperoxidase (MPO) and proteinase 3 (PR3) ANCA specificity (1). There is limited information about the characteristics of MPO- AAV and PR3-AAV in children. Objectives The objective of this study was to review the characteristics of MPO-AAV and PR3-AAV at a children’s hospital in multi-ethnic Central California, United States. Methods We performed a retrospective case review of patients less than 18 years of age diagnosed with AAV at a tertiary care children’s hospital in Central California in United States from January 1, 2010 to March 31, 2021. Cases were identified from electronic health records using ICD-9 and ICD-10 codes for vasculitis. Records were reviewed for a diagnosis of AAV based on ACR/EULAR classification criteria. Demographic and clinical data including laboratory parameters including ANCA specificity, treatment, and outcomes were collected. Continuous data were expressed as a median and interquartile range, categorical data as frequency and percentages. Chi-square and Mann-Whitney U tests were used for statistical comparison as appropriate. Results Eighteen cases of pediatric AAV were identified, of which 10 (55.5%) patients had MPO-AAV and 8 (44.4%) had PR3-AAV. All patients who were MPO positive were diagnosed with MPA. Among PR3-AAV cohort, 7 patients were diagnosed with GPA and 1 patient received diagnosis of MPA. The median age at diagnosis was 12.6 years (IQR 10.1-15.4) in patients with MPO-AAV and 14.8 years (13.8-16.7) in children with PR3-AAV. In MPO-AAV cohort, 90% (n=9) were female, meanwhile 37.5% (n= 3) of patients diagnosed with PR3-AAV were female (p=0.02). Significantly higher proportion of patients diagnosed with MPO-AAV were from racial and ethnic minority groups (n=10, 100%) which included Hispanic (8), Asian (1) and other (1). In comparison, patients with PR3-AAV were predominantly white (n= 7, 87.5%; p &lt;0.01). Median length of hospital stay was 19 days (IQR=12.8-41) in patients with MPO-AAV and 14 days (IQR=9.5-21.8) in patients with PR3-AAV. Rate of ICU admission was 60% in MPO-AAV cohort and 37.5% in PR-3 cohort, although this was not statistically significant. 50% (n=5) of patients in MPO-AAV cohort required dialysis and 25% (n=2) in PR3-AAV cohort. Peak creatinine was higher in MPO-AAV cohort (7.4, IQR 1-13.4 versus 2, IQR 0.7-3.7 mg/dL), although it did not reach statistical significance (p=0.1). PR3-AAV group had significantly higher levels of C-reactive protein (22.9, IQR=7.05-26.3) compared to MPO-AAV cohort (2.25, IQR=0.3-6.2; P=0.02). ENT involvement was more frequent in PR3-AAV cohort (87.5% versus 10%). All patients received treatment with high dose corticosteroids at diagnosis. Other immunosuppressive therapy included cyclophosphamide (40% in MPO-AAV cohort and 75% in PR-3 AAV cohort), rituximab (40% MPO-AAV cohort and 0% in PR-3 AAV cohort), cyclophosphamide and rituximab (10% in MPO-AAV cohort and 25% in PR-3 AAV cohort). Two deaths were reported in MPO-AAV cohort, related to Aspergillus pneumonia and pulmonary hemorrhage. Conclusion Our study reviews characteristics of pediatric MPO-AAV and PR3-AAV in the Central California of United States. We observed a more frequent diagnosis of MPO-AAV in racial/ethnic minority children. Limitations of our study include small sample size. This study highlights the need for further research to understand the impact of ethnicity and MPO and PR3 positivity on pediatric AAV presentation, disease activity and outcomes. References [1]Hilhorst, Marc et al. Proteinase 3-ANCA Vasculitis versus Myeloperoxidase-ANCA Vasculitis. Journal of the American Society of Nephrology: JASN vol. 26,10 (2015): 2314-27. Disclosure of Interests None declared